The present invention relates to a scraper device for conveyer belt systems, the device having a number of identical scraper elements that extend one beside another substantially over the width of the conveyer belt, with each scraper element basically comprising: a metal scraper or doctor blade that is in resilient engagement with the conveyer belt; an arm that supports the doctor blade; and a resilient articulation that is disposed at the free end of the support arm, the stationary part of the articulation being releasably secured to a common support tube that extends transverse to the direction of conveyance and parallel to the conveyer belt, the scrapersupport arm being deflectable about an axis that extends substantially parallel to the support tube, the scraping edge of the doctor blade being so positioned that the base of a perpendicular line from the axis of the articulation to the conveyer belt lies on the approach side of the belt at a slight distance ahead of the point of engagement of the scraping edge, the support tube being so secured at its ends to retaining means that the distance between such tube and the conveyer belt is adjustable.
Scraper devices of this general kind are known, for example, from DE-OS No. 32 11 626. If scraper devices of this kind are to provide satisfactory cleaning, the individual scraper elements that make up a device must each have their doctor blade in resilient engagement with the belt at substantially the same preloading or biasing for each blade, and they must be able to retain this ability for a very long peiod of operation. Since a conveyer belt is usually stressed more heavily at its center than at its edges, the scraper elements at the center are of course subject to greater wear than are the outer scraper elements. Consequently, the more worn scraper elements require periodic adjustment of their doctor blades to ensure that the blade engages the belt at the required pressure.
As a rule, all the scraper elements of a device can be simultaneously adjusted by way of their end retaining means even when the belt is running; however, the adjustment of individual scraper elements of the known construction, while the belt is running, is possible either only with great difficulty or not at all. The main reason for this is the nature of the adjustable securing of the individual scraper elements to the common transverse cross-member. In the aforementioned known scraper device, such securing comprises a clampable clip or the like that is mounted on a tubular cross-member and can be secured by frictional engagement. When a clip is released for adjustment purposes while the belt is running, the scraper element is entrained by the moving belt simultaneously with its release, and is pivoted outwardly and downwardly.
In the type of adjustable securing of a scraper element to a tubular cross-member just described, the complete element orbits about the axis of the tubular member while the blade is being adjusted. This leads to another serious disadvantage in addition to the drawback already referred to. When a scraper device is installed, its elements are adjusted in such a way that the scraping edges of the individual blades are substantially in alignment with one another. If individual blades wear prematurely and the corresponding elements are adjusted individually, the orbiting movement results in a lateral shifting of the point where the edge engages the belt, i.e., the scraping edges of the adjusted blades cease to be in alignment with the other, i.e. unadjusted, blades. Consequently, the very narrow gap between adjacent blades necessarily increases at the joints, so that there is a risk that the material that is to be scraped-off will pass through the larger gaps.
It is therefore an object of the present invention to design the releasable securing of the individual scraper elements to the common support tube of a scraping device for conveyer belt systems in such a way that the aforementioned drawbacks are obviated, i.e., the securing has as its first requirement that the adjustment of individual doctor blades is simple and safe, even when the belt is moving. Furthermore, there must be no shift in the alignment of the adjusted scraper elements, and the securing arrangement must be compact.